The minuteness of pattern has been progressed together with the increase in the degree of integration of semiconductor elements. Photolithography using light as exposure source has been used there. At present, reduction step-and-repeat projection exposure method is the main current because of high resolution and excellent alignment accuracy. There are problems in fine pattern formation by a single-layer resist method using photolithography, that is, change or variation in pattern dimension caused by local change in resist film thickness due to the unevenness of substrate or substrate topography (bulk effect), and dwindling in pattern dimension caused by local overexposure on resist due to scattering light from side wall part of substrate topography (notching effect). Furthermore, since the reduction step-and-repeat projection exposure uses refractive optics, monochromatic light is used as exposure source, and the use of monochromatic light causes another problem.
Namely, there occurs interferences one another between incident beam to a resist, reflected beam from a resist surface, and reflected beam from a resist/substrate interface, which causes change in effective quantity of light absorbed in the resist according to slight change in resist film thickness at a period of .lambda./2n (.lambda.: exposing wavelength, n: refractive index of resist), which in turn causes change in resist pattern dimension (multiple in-film reflection effect), or causes periodical distribution of light strength in the direction of resist thickness, which in turn causes corresponding corrugation in the section of resist pattern after development (standing wave effect). All of these produce change in resist pattern dimension and poor resolution.
As ways to solve these problems of the prior single-layer resist method, there have been proposed a multi-layer resist method, an ARC method and an ARCOR method. In the multi-layer method, however, there are problems such as a number of process steps and low throughput, since three resist layers are formed and thereafter pattern is transferred to form resist pattern used as mask. In the ARC method, there are problems such as much amount of side etching and much decrease in dimensional accuracy thereby since an anti-reflection film formed underneath resist is wet-etched by development. The ARCOR method is a method to suppress multi-reflection in a resist film by coating one layer or multiple layers of an interference-type anti-reflection film comprising oil-soluble perfluoroalkyl compound on the resist film. The anti-reflection film used, however, cannot be coated as an aqueous solution and thus it is coated as a solution in a solvent. Therefore, the anti-reflection film cannot be removed of course by rinsing, which leads to problems that it makes the procedure complex, and that the number of process steps and materials used increase. The multi-layer resist method is described in Japan Patent Laid-Open Specification Sho 51-10775 etc. The ARC method is described in Japan Patent Laid-Open Specification Sho 59-93448 and the ARCOR method is described in Japan Patent Laid-Open Specification Sho 62-62520.
The present invention is made under such background, and an object of the present invention is to provide a composition for forming surface anti-reflection film on photoresist film at the time of formation of a pattern. Furthermore, another object is to provide a method to improve change in a resist pattern dimension and resolution at the time of formation of a pattern, wherein the composition for forming anti-reflection film can be coated as an aqueous solution, and wherein the obtained anti-reflection film can be removed after formation of resist pattern by a convenient method such as rinsing and alkali development, which are usual post-treatments.